The First Crusade was a military campaign led by the Western Christianity from 1096 to 1099 to reclaim the Holy Lands which were taken in the Muslim victory of the Levant, which resulted in the recapture of Jerusalem. Pope Urban ll launched the campaign in 1095 with the focus of responding to an appeal from Byzantine Emperor Alexios l Komnenos, who requested western volunteers come to help ward of the invading Seljuq Turks from Anatolia.

The Christian reconquest of the sacred city of Jerusalem and the freeing of the Eastern Christians from Islamic rule became ultimately became the principal goal. Many nations of Western Europe travelled over land and sea, firstly to Constantinople and then on towards Jerusalem with the peasants outnumbering the knights. The peasants and knights were split into two armies, with the peasants not being as well trained as the knights they failed to reach Jerusalem.

An assault was launched onto the city when the knights arrived in Jerusalem, seizing the city in July 1099 and forming the crusader states of the Kingdom of Jerusalem, the Principality of Antioch, the Country of Edessa and the County of Tripoli. The First Crusade was mainly concerned with Jerusalem, which had not been under Christian authority for 461 years and the Crusader army denied the Byzantine Empire control of the land.

The First Crusade was in response to the Muslim conquests and was proceeded by the Second Crusade to the ninth Crusade, and the benefits made lasted for less than 200 years. It also was the first major advancement towards restoring international trade in the West since the decline of the Western Roman Empire. The Crusades have been most commonly linked to the social and political situation in the 11th century Europe. This involved the rise of a reform movement with the papacy, and the religious and political confrontation of Christianity and Islam in the Middle East and Europe. Christianity had expanded throughout Africa, Europe and the Middle East in Late Antiquity, but by the early 8th century it had become restricted to Europe and Antatolia after the Muslim conquests.

Umayyad Caliphate had overcome Syria, Egypt and North Africa from the Christian Byzantine Empire, and Spain from the Visigothic Kingdom. The Ummayad empire eventually deteriorated and a number of smaller Muslim kingdoms emerged, that being the Aghlabids, whom attacked Italy in the 9th century. The Principality of Catalonia, Pisa and Genoa began to attack various Muslim kingdoms for command of the Mediterranean Basin, depicted by the Mahdia campaign and conquests at Majorca and Sardinia.

The First Crusade established the “crusader states” of Edessa, Antioch, Jerusalem, and Tripoli in Palestine and Syria. Those who had survived were treated as heroes back home in Western Europe, Jerusalem. The establishment of the crusader states in the east eased Seljuq pressure on the Byzantine Empire and resulted in a period of relative peace and prosperity in the 12th century.

The political instability and the dividing of the Great Seljuq Empire meant that it had prevented a coherent defence against the Latin states. There remained cooperation difficulties for many decades to come, from Egypt to Baghdad there were calls for the removal of the crusaders, which resulted in the recapture of Jerusalem under Saladin later on in the century.